According to a report from Pitchfork, the pop star played an acoustic version of her hit song "Delicate" alongside Hayley Kiyoko. The pair sang together, inviting the audience inside Town Hall in New York City to join in.

Fans were blindsided by Swift's appearance on the Ally Coalition stage. Many snapped videos and cheered her on from their spots in the audience.

The performance came on the coattails of Swift's album, reputation, taking album of the year on Billboard's 2018 year-end list. This is the third time she's received the accolade.

Wednesday's Ally Coalition benefit was the fifth annual iteration of the event. It included performances from Bleachers, Mitski, Rostam, Regina Spektor, fun. frontman Andrew Dost and Lana Del Rey, who performed a new single with help from Antonoff. Attendees were also treated to a stand-up set from former Saturday Night Live star Sasheer Zamata.